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Facial Ontogeny and Variation in Australopithecus afarensis: Implications for Hominin Diversity
No full textInvestigating morphological variation is essential for understanding hominin taxonomic diversity and phylogeny, particularly in Australopithecus afarensis (c. 3.9–3.0 Ma), whose expanded fossil sample enables comparisons with ancestral, contemporaneous, and descendant taxa. Hominin fossils from Hadar (Ethiopia) and Laetoli (Tanzania) were assigned to Au. afarensis in the 1970s and exhibit substantial variability and sexual dimorphism. However, the extent of this variation and the taxon’s relationship to the older Au. anamensis (c. 4.3–3.8 Ma) and other contemporaneous hominins remain debated. Recent fossil discoveries and advancements in imaging and reconstruction techniques allowed us for a holistic examination of facial ontogeny and variation in Au. afarensis. In Chapter 1, I provide a general background to the research questions. In Chapter 2, I investigate facial variation and sexual dimorphism in extant great apes to establish a comparative framework for interpreting fossil hominin variation (Chapters 3 and 4). Many traits previously considered diagnostic of Au. afarensis show substantial intraspecific variability in great apes. Linear metric analyses revealed a high degree of variation and sexual dimorphism in Pongo and Gorilla, largely size-related, while Pan species exhibit lower variation. Notably, P. paniscus shows minimal variation and sexual dimorphism, with females exhibiting greater variability. African apes exhibit shared patterns of variation; deviations from these patterns in hominin assemblages may signal taxonomic heterogeneity. In Chapter 3, I analyze newly discovered fossils and quantify facial variation in Au. afarensis. Traits once considered uniquely diagnostic of the taxon show intra-specific variability and overlap with Au. anamensis and Au. deyiremeda. Au. afarensis exhibits a high coefficient of variation, comparable to that of gorillas and exceeding bonobos and chimpanzees, suggesting it includes either a taxonomically heterogeneous sample, accumulated temporal variation, or a pattern of variability akin to Gorilla. In Chapter 4, I examine facial ontogeny in Au. afarensis, finding that many diagnostic features appear early in development, foreshadowing adult variation. Traditional and geometric morphometric analyses reveal significant intra- and interspecific variation along a shared growth trajectory, resulting in distinct size and shape ranges in Au. afarensis and African apes, with divergent patterns in orangutans. Juveniles, DIK-1-1 and A.L. 333-105, differ in facial traits and overall profile. In shape space, DIK-1-1 aligns close to the Pan juveniles, while A.L. 333-105 groups closer to Pongo, though their differences fall within the expected intraspecific range for Au. afarensis. In conclusion, Au. afarensis exhibits greater adult and juvenile variation than previously recognized, with some morphotypes resembling Au. deyiremeda. While the Au. anamensis cranium, MRD-VP-1/1, shows distinct morphology mainly in the feeding apparatus, some features are shared with Au. afarensis, suggesting an ancestor-descendant relationship but more complex evolutionary transitions among Au. anamensis, Au. afarensis, and contemporaneous hominins. These findings highlight the importance of reexamining fossils using advanced imaging tools, investigating ontogeny and temporal trends, and incorporating new discoveries to refine interpretations of hominin diversity and phylogeny
Is Money a Public Good?
Get PDFWhy has contemporary political theory been silent on money? The answer Stefan Eich provides in his brilliant book The Currency of Politics begins with John Rawls. Rawls’s silence on money and monetary policy is, for Eich, mostly a result of indifference—an indifference that reflected the fact that Rawls took for granted a “confident postwar context” characterized by affluence and a relatively stable international monetary system (181). The real “silent revolution,” as Eich calls it (20, 177), comes after Rawls. By the 1980s, the international monetary regime undergoes drastic changes, including the lifting of capital controls and the rise of central bank independence. As Eich insightfully argues, this depoliticization of money was itself a political strategy. By letting consequential economic decisions remain outside the realm of political contestation, states tried to avoid excessive pressures. According to Eich, major political theorists, including Jürgen Habermas and Michael Walzer, fell prey to this neoliberal logic. In part because of the inflationary demands that a democratization of the economy would imply, such thinkers grew skeptical of the possibility of any such democratization. The disappearance of money from political theory was one of the consequences of this more general turning away from economic democracy (197–99)
Model averaging and double machine learning (replication data)
No full textThis is the replication repository for the paper "Model averaging and double machine learning" by Achim Ahrens, Christian Hansen, Mark Schaffer and Thomas Wiemann (Journal of Applied Econometrics)
Differential impact from individual versus collective misinformation tagging on the diversity of Twitter (X) information engagement and mobility
Get PDFFears about the destabilizing impact of misinformation online have motivated individuals and platforms to respond. Individuals have increasingly challenged others’ online claims with fact-checks in pursuit of a healthier information ecosystem and to break down echo chambers of self-reinforcing opinion. Using Twitter (now X) data, here we show the consequences of individual misinformation tagging: tagged posters had explored novel political information and expanded topical interests immediately prior, but being tagged caused posters to retreat into information bubbles. These unintended consequences were softened by a collective verification system for misinformation moderation. In Twitter’s new feature, Community Notes, misinformation tagging was peer-reviewed by other fact-checkers before revelation to the poster. With collective misinformation tagging, posters were less likely to retreat from diverse information engagement. Detailed comparison demonstrated differences in toxicity, sentiment, readability, and delay in individual versus collective misinformation tagging messages. These findings provide evidence for differential impacts from individual versus collective moderation strategies on the diversity of information engagement and mobility across the information ecosystem
Unveiling the Impacts of Charge/Discharge Rate on the Cycling Performance of Li-Metal Batteries
Get PDFLithium metal batteries (LMBs) offer superior energy density and power capability but face challenges in cycle stability and safety. This study introduces a strategic approach to improving LMB cycle stability by optimizing charge/discharge rates. Our results show that slow charging (0.2C) and fast discharging (3C) significantly improve performance, with a multilayer LMB retaining over 80% capacity after 1000 cycles. Fast discharge rates promote lithium plating beneath the SEI layer, suppressing its growth and improving Coulombic efficiency, whereas slow discharge rates facilitate lithium plating above the SEI, leading to SEI accumulation. We propose a rational hypothesis linking SEI conductivity and cycling conditions and introduce an intermittent pulse discharge protocol to emulate electric vehicle applications, further improving the stability. These optimized cycling strategies enhance the LMB lifespan, utility, and safety, paving the way for broader market adoption in the years ahead
Geochemical Interaction between CO<sub>2</sub> and caprock for safe carbon sequestration
Get PDFCarbon dioxide (CO2) emission into the atmosphere from human activities and industrial processes continues to pose a major environmental and health threat to public safety worldwide with many governments launching initiatives to reduce the impact of CO2 emission. Carbon dioxide capture and storage (CCS) is a process of separating CO2 from industrial facilities and other point sources and injecting it in a deep geological formation such as depleted oil and gas reservoirs for long-term storage [1]. Usually, CO2 is injected into a deep formation at a depth more than 1000 m where in-situ pressure and temperature is above the critical point for CO2 (31.1
Progesterone induces meiosis through two obligate co-receptors with PLA2 activity
Get PDFThe steroid hormone progesterone (P4) regulates multiple aspects of reproductive and metabolic physiology. Classical P4 signaling operates through nuclear receptors that regulate transcription. In addition, P4 signals through membrane P4 receptors (mPRs) in a rapid nongenomic modality. Despite the established physiological importance of P4 nongenomic signaling, the details of its signal transduction cascade remain elusive. Here, using Xenopus oocyte maturation as a well-established physiological readout of nongenomic P4 signaling, we identify the lipid hydrolase ABHD2 (α/β hydrolase domain-containing protein 2) as an essential mPRβ co-receptor to trigger meiosis. We show using functional assays coupled to unbiased and targeted cell-based lipidomics that ABHD2 possesses a phospholipase A2 (PLA2) activity that requires mPRβ. This PLA2 activity bifurcates P4 signaling by inducing clathrin-dependent endocytosis of mPRβ, resulting in the production of lipid messengers that are G-protein coupled receptor agonists. Therefore, P4 drives meiosis by inducing an ABHD2 PLA2 activity that requires both mPRβ and ABHD2 as obligate co-receptors
Significant Impacts of Increasing Aridity on the Arid Soil Microbiome
Get PDFGlobal deserts occupy one-third of the Earth’s surface and contribute significantly to organic carbon storage, a process at risk in dryland ecosystems that are highly vulnerable to climate-driven ecosystem degradation. The forces controlling desert ecosystem degradation rates are poorly understood, particularly with respect to the relevance of the arid-soil microbiome. Here we document correlations between increasing aridity and soil bacterial and archaeal microbiome composition along arid to hyperarid transects traversing the Atacama Desert, Chile. A meta-analysis reveals that Atacama soil microbiomes exhibit a gradient in composition, are distinct from a broad cross-section of nondesert soils, and yet are similar to three deserts from different continents. Community richness and diversity were significantly positively correlated with soil relative humidity (SoilRH). Phylogenetic composition was strongly correlated with SoilRH, temperature, and electrical conductivity. The strongest and most significant correlations between SoilRH and phylum relative abundance were observed for Acidobacteria, Proteobacteria, Planctomycetes, Verrucomicrobia, and Euryarchaeota (Spearman’s rank correlation [rs] = >0.81; false-discovery rate [q] = ≤0.005), characterized by 10- to 300-fold decreases in the relative abundance of each taxon. In addition, network analysis revealed a deterioration in the density of significant associations between taxa along the arid to hyperarid gradient, a pattern that may compromise the resilience of hyperarid communities because they lack properties associated with communities that are more integrated. In summary, results suggest that arid-soil microbiome stability is sensitive to aridity as demonstrated by decreased community connectivity associated with the transition from the arid class to the hyperarid class and the significant correlations observed between soilRH and both diversity and the relative abundances of key microbial phyla typically dominant in global soils. Importance: We identify key environmental and geochemical factors that shape the arid soil microbiome along aridity and vegetation gradients spanning over 300 km of the Atacama Desert, Chile. Decreasing average soil relative humidity and increasing temperature explain significant reductions in the diversity and connectivity of these desert soil microbial communities and lead to significant reductions in the abundance of key taxa typically associated with fertile soils. This finding is important because it suggests that predicted climate change-driven increases in aridity may compromise the capacity of the arid-soil microbiome to sustain necessary nutrient cycling and carbon sequestration functions as well as vegetative cover in desert ecosystems, which comprise one-third of the terrestrial biomes on Earth.</p
Metal–organic layer delivers 3-bromopyruvate to mitochondria for metabolic regulation and cancer radio-immunotherapy
Get PDFAbnormal cancer metabolism causes hypoxia and immunosuppression, limiting the anti-tumor efficacy of radiotherapy. Herein, we report a positively charged, mitochondria-targeted nanoscale metal–organic layer conjugated with 3-bromopyruvate (BP), BP/Hf12-Ir, for metabolic reprogramming and radiosensitization. BP/Hf12-Ir disrupts oxidative phosphorylation and glycolysis, reducing energy production and alleviating hypoxia to enhance radiotherapy and anti-tumor immunity. BP/Hf12-Ir in combination with X-ray irradiation inhibits tumor growth by 95% and prevents lung metastasis in mouse models. When further combined with immune checkpoint blockade, this treatment induces robust anti-tumor immunity, achieving 98% tumor growth inhibition